New Delhi: Women who work nightshifts are more likely to suffer from moderate or severe asthma compared to women who work in the daytime, according to a study of more than 270,000 people.  

However, the study, published in ERJ Open Research, found no such link between asthma and working nightshifts in men. The risk of asthma in men did not alter according to whether they worked days or nights.

Women who only work nightshifts were around 50 per cent more likely to suffer from moderate or severe asthma compared to women who only work in the daytime.

"Asthma disproportionately affects women. Women generally have more severe asthma, and a higher rate of hospitalisation and death from asthma compared to men,” said Dr. Robert Maidstone from the University of Manchester, UK.

"This is the first study to evaluate sex differences in the relationship between shift work and asthma. We found that permanent nightshift workers had higher odds of moderate-severe asthma when compared to corresponding day workers,” he added.

The study builds on previous research which found a higher risk of moderate or severe asthma in nightshift workers.

To probe further, the team included a total of 274,541 working people and found that 5.3 per cent of those had asthma, with 1.9 per cent suffering from moderate or severe asthma (meaning they were taking an asthma-preventer inhaler and at least one other asthma treatment, such as an oral steroid).

Overall, the research found that women who work shifts are more likely to have asthma.

While the research did not explain the link between shift work and asthma, the researchers said, “it could be because shift work disrupts the body clock, including the levels of male and female sex hormones”.

High testosterone has previously been shown to be protective against asthma, so lower testosterone in women could play a role. Alternatively, men and women work different types of shift jobs, and this could be a factor, the researchers said.

In postmenopausal women, the risk of moderate or severe asthma was almost doubled in night workers, compared to day workers, in those not taking hormone replacement therapy (HRT).

"Our results suggest that HRT might be protective against asthma for nightshift workers, however further research is needed to test this hypothesis in prospective studies and randomised controlled trials," Maidstone said.

The researchers next plan to study whether sex hormones play a role in the relationship between shift work and asthma. (IANS)